Circuit element for tuning an electric circuit over a plurality of frequency bands



May 31, 1949. F. H. GUSDORF ETAL 2,471,523

CIRCUIT ELEMENT FOR TUNING AN ELECTRIC CIRCUIT OVER A PLURALITY OF FREQUENCY BANDS Filed April 17, 1946 2 Sheets-Sheet l Flg. 1. I

FRIDERZKf/fiNDRIK GUSDOZZF AZfiXAN 012E [YOROW] T Z IN V EN TORS.

BY%-g ATTORNEY May 31, 1949. F. H. GUSDORF ET AL 2,471,523

CIRCUIT ELEMENT FOR TUNING AN ELECTRIC CIRCUIT pVER A PLURALITY OF FREQUENCY BANDS Filed April 1'7, 1946 2 Sheets-Sheet 2 I I/ I l 1 AZFXANDRF EJ120710 T Z I N VEN TORS AT T ORA El Patented May 31, 1949 CIRCUIT ELEMENT FOR TUNING AN: ELEC TRIC CIRCUIT OVER A PLURALITY. OF

FREQUENCY BANDS Frederik Hendrik Gusdorf and Alexandre Horowitz, Eindhoven, Netherlands, assignors', by

mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application April 17, 1946, Serial No. 662,680 In the Netherlands November 4, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires November 4, 1961 11 Claims. 1

This invention relates to a device comprising a tunable electric circuit including a variable condenser which is adjustable in two differentmanners independent of each other.

It is known to adjust different tuning ranges,

for example of a transmitter, a receiving set or" uring ranges which either. adjoin or even overlap,

each other, or in a certain number of wave or frequency bands which are but very narrow relatively to the whole region of wavelengths or frequencies in which they are located and which they do not cover entirely. This applies to the so-called band-spread, which is frequently used in the reception of short waves and constitutes an important domain of application of the ob-' ject of the present invention.

In the known devices for the above-described band-spread it was already known to control the inductance and/or the capacity of a tunable cir- 5 cuit in fixed steps and then to efiect the bandspreading by means of a small variation in inductance or capacity. In this case the principal problem was the obtainment of a uniform bandspread over all bands, i. e. the obtainment of an equal length of scale for theband tuning'with bands of different wavelengths, for example in' the 49 metre band as well as in the 13 metre band.

Equal width of band-spread could to a certain extent be obtained for bands of smaller as well as larger wavelength by controllingone' element of the tunable circuit in steps and the other element of the tunable circuit by means of band tuning, i. e. by means of a Very'small variation. The last-mentioned variation thus always constitutes the same percentage of themean value of the capacity or inductance included in the tunable circuit and this impliesthat also the variation in wave-length or frequency of the tuned circuit always amounts to the same percentage of the mean wavelength or frequency'of the circuit.

Consequently, the above-stated tuning was realisable either bymeans of intermittent adjustment of the inductance and band tuning of. the capacity, or by means of intermittent tuning of the capacity and band tuning of .the inductance.

Apart from the mechanical problems which these solutions involved the most. important 2 fundamental difficulty was that in all these cases only one continuous tuning in the band was available and for all. bands thedetermination of the bandwidth was given once and for all by the construction chosen. This was particularly disadvantageous, since-.the width ofa definite tuning range or-a definite wave-band wasnot always required to correspond with the same percentage difference inwave-length or frequency.

The invent-ion has for its purpose to permit a tuning in different measuring ranges or wavebands, the operation of the tuning member being adapted to the frequency of the measuring range or wave-bandin a highly simple and accurate manner independently ofthe mechanism by means of which the tuning member considered is operated.

According to the invention, to this end the driving mechanism for one displacement of the condenser is coupled to a. switch orany other member for selecting the wave-length or frequency region to be switched-in, whereas the driving mechanism for the other displacement of the condenser constitutes the adjusting mechnism for the tuning within this range, the construction being such that for each of these regionsthe capacity range of the last-mentioned displacement is so adjusted by the first-mentioned displacement as to correspond with the A wavelength or frequency, range .to be adjusted.

The advantage of a new degree of liberty in determining the various measuring ranges or wave-bands is thus obtainedsince, even after the device is completed, the tuning curve of each range may be influenced at any moment, for

-example for the exact determination of the location and the width of band-spread of the graduation, by means of separate members to be readjusted. Moreover, it now becomes possible for the tuning curve to be influenced entirely automatically in accordance with the value of the fixed capacities or inductances in the tunable circuit, i. e. entirely in accordance with the wavelength or frequency of the range to be switchedin According to theiinvention, the various tuning ranges may be obtained. by utilising solely the capacity of the doubly adjustable condenser as a tuning capacity, which gives a very simple electric circuit. In this case one of the two dis- -p1acements will frequently be effected over a small percentage ofthe total displacement and must consequently be controlled by a tuning member having astroke length which is small but reproducible with great accuracy. The advantage of the invention. which consists inv obtaining each time a tuning range of which the variation in capacity amounts to the same percentage fraction of the mean tuning capacity of the circuit is here obtained automatically,

since in most cases in the different positions of the one displacement all the adjusted values of the other displacement will continue to exhibit the same ratio of capacity between each other.

On the other hand, it is possible to obtain a particularly advantageous operation of the tuning by dividing the tuning capacity into an intermittently adjustable part and a continuous doubly adjustable part, the driving mechanism for one of the displacements of the last-mentioned part cooperating with the device, by means of which the first-mentioned part of the capacity is displaced intermittently.

The advantage is thus obtained that the doubly adjustable part of the capacity is very small and may operate in the manner of the band-spread condenser which has since long been usual in short-wave reception, while the control members for the intermittently adjustable part may be so constructed that in the most divergent measuring ranges or wave bands one always obtains the same length of scale for the measuring apparatus, the receiving set or the transmitter.

If an intermittently adjustable capacity must co-operate with the doubly adjustable capacity,

it is advisable that the former should be obtained by looking a continuously adjustable condenser in each tuning range in the corresponding position of tuning so that it is not necessary to utilise a separate switch for the tuning ranges and switch contacts in the tuning circuit may be avoided. Moreover, it is then possible for each of these fixed condenser positions to be separately re-adjusted mechanically and thus for the different measuring ranges to be adjusted separately.

In this case it is possible for the stators of the above-mentioned continuously adjustable condenser and of the doubly adjustable condenser to be made in one piece, since the stator then need constitute but a small protrusion of the stator of the other condenser so that a highly compact construction is obtained.

In a device according to the invention it is particularly advantageous that the doubly adjustable condenser used be one, for example, having half-cylindrical electrodes which may be -angularly shifted relative to each other and shifted in the axial direction as well so that two degrees of variation independent of each other are afforded in accordance with the principle of the invention.

In this case the rotary movement is particularly suitable for driving by means of a normally rotating tuning mechanism, whereas the variation in capacity due to displacement of the electrodes in the axial direction is particularly fit to be controlled by means of mechanical transmission members having intermittent variation.

For tuning in a narrow frequency band it is advantageous to utilise a rotary electrode condenser comprising only one or few rotor plates and a set of stator plates cooperating therewith, which are placed in the normal manner at right angles to the shaft and whose plate distance may be varied in the axial direction.

A condenser of this type has the small variation in capacity required for the purpose, while the variation in the mean capacity may be very easily obtained byv means of a small axial displacement of the rotor, which is very well suitable for cooperation with the driving members of very small stroke.

When use is made of a rotary and slidable electrode condenser of the type above-described it is possible to use the driving mechanism of the condenser for the tuning in the measuring range or the wave band and to couple the sliding mechanism to the switching device for the measuring ranges or wave bands, or inversely. However, driving of the sliding movement by the switching device and tuning within the region or the band chosen by means of the rotary mechanism of the condenser will generally be preferred. this being most suitable for the methods of driving used in both cases.

A very suitable method of driving for the adaptation of the tuning width of the doubly adjustable condenser to the tuning range chosen consists in the use of a rotary member which is driven by the intermittently operating switching device and has, for example, the form of a disc, whose circumference comprises a certain number of adjustable pins each of which corresponds to a definite switch position and in this position alternately co-operates with the same of the two driving devices of the doubly adjustable condenser. Such a rotary member is known in technics as a revolving head and is particularly adapted to be used in a drive according to the invention, since in this case it is possible for the capacity variation, or the mean capacity of the doubly adjustable condenser to be readjusted separately at any moment for any switch position of the tuning range switch.

It is also possible to cause the mechanism for the control of the capacity variation or the mean capacity of the doubly adjustable condenser to co-operate also with more than one intermittently operating switching device for the tuning ranges. In this case a very simple control of the device is ensured even when more than one method is used for the intermittent variation of the tuning elements.

For the above-described purpose the mechanism for the control of the capacity variation or the mean capacity of the doubly adjustable condenser may co-operate with a so-called differential lever which is connected to two different switching devices, one of which for example intermittently varies the inductance and the other the fixed capacity of the tuning circuit.

In one preferred embodiment of the invention the differential lever (co-operates with cam discs which are mounted on the shafts of the switching devices so that owing to the free choice of the cam shape it is possible to obtain the desired positions of the doubly adjustable condenser for any combination of the positions of the two switching devices. When more than one differential lever is used in combination the doubly adjustably condenser may also be controlled by more than two switching devices.

In order that the invention may be more clearly understood and readily carried into efiect, it will be described more fully by reference to the accompanying drawings.

Fig. 1 shows the construction of a rotatable and slidable electrode condenser according to the invention Which is combined with a normal variable condenser.

Fig. 2 shows a cross-section view along the axis II--II of the condenser shown in Fig. 1.

Figs. 3 and 4 show this construction, likewise in two projections and partly in section, for

the rotary and slidable electrode condenser separately.

'Fig. 5 shows a rotary and slidable electrode strips 3 which are fastened together for example by spot welding. These head plates comprise a" fixed ball-bearing 4 and a resilient ball-bearing 5; which support a condenser shaft 6 and acounterweight l, which shaft carries a double set of rotor plates 8 which co-operate with stator plates 9 made in one piece, for example by diecasting or milling. The said head plates com prise, in addition, bearing bushes ill and H, in which the shaft l2 of a rotary and slidable elec trode condenser can rotate and slide, which shaft may be rotated by means of a driver 13 anda pin l4 and may be pressed-in against the action of a spring I! by pressing the steel. ball l6 adjustably fastened in the front of a cap nut l5. It is thus possible to vary the depth over which the fixed electrode ill of each slidable condenser section, which forms one piece with the stator 9"of' the rotary condenser, co-oper'at'es with the" movable electrode t9.

Fig. 2 shows the sections of ceramic rods which are passed through the two stator bodies 9 of the variable condenser so that the latter and hence also the fixed electrodes 28 of the rotary and slidable electrode condenser are arranged in an insulated manner. In this manner the two condensers jointly form one unit, one part of which may serve for the tuning of the circuits over a comparatively large wave range, while band tuning in definite wave bands to be adjusted may be effected by rotating the rotary and slidable electrode condenser 18-49, whose electrodes in accordance with the position of the band switch are more or less collapsed in order to bring the length of scale for each band at the required size. It is also possible to make the displacement of the rotary andslida'ble electrode condenser dependent on more than one waverange switch.

Figs. 3 and 4 show separately a part of the shaft ll of the rotary and slidable electrode condenser, together with a movable electrode 19 and The depth of a fixed electrode l8 oi the latter. sliding of the he.lfcylindrical part 23 of the electrode H] in the half-cylindrical gap 21 of the electrode I8 is here designated by an arrow 22.

Fig; 5 shows a double band-spread condenser comprising stator plates 3! of half-circular sec tion which are arranged in an insulated manner in a condenser casing 32 in which the condenser shaft 33 is mounted in a rotary and slidable manner, the spring at always sliding the shaft as far as possible to the right while the driver 35 serves as an intermediate member for the transmission of the rotary drive of the rotor plates 36 of therotary andv slidable electrode condenser. The spacing at of the condenser electrodes may be" Varied by varying a revolving head compris ing adjustable pins 3'! each of which correspondsto one of the contacts 4'! arranged on. contact wafers 48 to cooperate with contact arms 50' of the band switch 39 which is mechanically coupled to the revolving head-38b t meansof gears 40 I the shaft 46 is rotated and moves the switch arms 50 to band selecting positions.

In the left-hand condenser section is indicated in dotted lines in M and 42 how a second set of condenser plates would have to be placed at a comparatively large distance from the first set (3i and 36), since otherwise in the case of displacement of the rotor to the right th increase in capacity between 36 and 4! would eliminate the increase in capacity between 3! and 36. This means that the longitudinal dimension of the condenser would inadinissibly increase even with more than two sets of plates.

Fig. 6 shows schematically how a tuning inductance 5| is provided with tappings 52 for different wave-ranges and is adjustable to different wave ranges by means of a wave-range switch 53; The same is the case with three different fixed condensers 54, 55, 5c, which may be a1- ternately switcheddn by means or" the waverange switch 51. One side of the inductance and of each of the condensers is connected to earth, whereas the two wave-range switches jointly constitute the voltage terminal of the tuning circuit thus constituted. The two wave-range switches operate by means of cam discs 58, 59 on a differential lever 60 which controls the displacement of the rotary and slidable electrode condenser 59 in the axial direction, which latter may operate as a band-spread condenser. The rotor of this condenser is earthed, whereas the stator is connected to the voltage terminal of the tuning circuit which is constituted by the inductance 5i jointly with one of the capacities 54 to 56 and the capacity of the rotary and slidable electrode condenser. Combining one of the positions of switch 53 with one of the positions of switch 51 now permits of switching-in nine different wave bands which then may be tuned by'shifting the band-spread condenser 53 over a scale range elongated to the full length of scale, if only'the ratio of the two limbs of the diiierential lever 60 and the dimensions of the cams on the discs 58 and 5B are chosen correctly.

An advantageous application of the principle of driving set out above is constituted by the so-called trimmer condenser in a transmitter, which serves to readjust the wave-length over a very small range of variation, for example in the case of interference by an adjacent transmitter. It is readily seen that this arrangement in a transmitter corresponds to the previously described band spread arrangement for use in receivers. In this case it also of importance that the trimmer condenser should have a suitable maximum value in accordance with the mean wavelength to which is tuned.

We claim:

1. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a first capacity adjusting means and a second capacity adjusting means independent of said first capacity adjusting means, a band selecting switch mechanically coupled to said first capacity adjusting means to adjust the capacity range of said second capacity adjusting means and select said circuit elements corresponding to'a desiredfrequency band, and means coupled to said second capacity adjusting means to continuously var-y the capacity of said capaci-- tor through said adjusted capacity range to tune over said desired frequency band.

2. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of inductive circuit elements, a variable capacitor having a first capacity adjusting means and a second capacity adjusting means independent of said first capacity adjusting means, a band selecting switch mechanically coupled to said first capacity adjusting means to adjust the capacity range of said second capacity adjusting means in steplike manner and select said circuit elements corresponding to a desired frequency, and means coupled to said second capacity adjusting means to continuously vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency band.

3. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of inductive circuit elements, a variable capacitor having a first continuous capacity adjusting means and a second continuous capacity adjusting means independent of said first continuous capacity adjusting means, a second variable capacitor adjustable in steps, a band selecting switch mechanically coupled to said first continuous capacity adjusting means and to said second variable capacitor to adjust the capacity range of said second continuous capacity adjusting means, adjust said second capacitor and select said circuit elements corresponding to a desired frequency band, and means coupled to said second continuous capacity adjusting means to vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency range.

4. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a first continuous capacity adjusting means and a second continuous capacity adjusting means independent of said first continuous capacity adjusting means, a second continuously variable capacitor arranged to be adjustable in predetermined steps, a band selecting switch mechanically coupled to said first continuous capacity adjusting means and to said second variable capacitor to adjust the capacity range of said second continuous capacity adjusting means, adjust said second capacitor in one of said steps and select said circuit elements corresponding to a desired frequency band, and means coupled to said second continuous capacity adjusting means to vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency range.

5. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a first continuous capacity adjusting means and a second continuous capacity adjusting means independent of said first continuous capacity adjusting means, a second continuously variable capacitor arranged to be adjustable in predetermined steps, said first and second variable capacitors having stator portions in common, a band selecting switch mechanically coupled to said first continuous capacity adjusting means and to said second variable capacitor to adjust the capacity range of said second continuous capacity adjusting means, adjust said second capacitor in one of said steps and select said circuit elements corresponding to a desired frequency band, and means coupled to said second continuous capacity adjusting means to vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency range.

6. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a stator and a complementary rotor of substantially semi-cylindrical construction, said rotor being angularly rotatable with respect to said stator to provide a first capacity adjusting means and axially slidable to provide a second capacity adjusting means independent of said first capacity adjusting means, a band selecting switch mechanically coupled to one of said capacity adjusting means to adjust the capacity range of the other of said capacity adjusting means and select said circuit elements corresponding to a desired frequency band, and means coupled to the other of said capacity adjusting means to continuously vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency band.

7. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a stator and a complementary rotor of substantially parallel plate construction, said rotor being angularly rotatable about an axis normal to the plane of the parallel plates with respect to said stator to provide a first capacity adjusting means and slidable along said axis to provide a second capacity adjusting means independent of said first capacity adjusting means, a band selecting switch mechanically coupled to one of said capacity adjusting means to adjust the capacity range of the other of said capacity adjusting means and select said circuit elements corresponding to a desired frequency band, and means coupled to the other of said capacity adjusting means to continuously vary the capacity of said capacitor through said adjusting capacity range to tune over said desired frequency band.

8. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a stator and a complementary rotor of substantially semi-cylindrical construction, said rotor being angularly rotatable with respect to said stator to provide a, first capacity adjusting means and axially slidable to provide a second capacity adjusting means independent of said first capacity adjusting means, a band selecting switch mechanically coupled to said second capacity adjusting means to adjust the capacity range of said first capacity adjusting means and select said circuit elements corresponding to a desired frequency band, and means coupled to said first capacity adjusting means to c0ntinuously vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency band.

9. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a stator and a complementary rotor, said rotor being angularly rotatable with respect to said stator to provide a first capacity adjusting means and axially slidable with respect to said rotor to provide a second capacity adjusting means independent of said first capacity adjusting means, a revolving head comprising a plurality of adjustable pin members arranged to present varying eifective lengths, a band selecting switch mechanically coupled to said revolving head simultaneously to rotate same and select said circuit elements corresponding to a desired frequency band, means engaging one of said pin members corresponding to the selected position of said band switch to adjust the capacity range of said first capacity adjusting means to correspond to said band of frequencies, and means coupled to said first capacity adjusting means to continuously vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency band.

10. An arrangement for tuning an electric circuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable eapacitor having a stator and a complementary rotor, said rotor being angularly rotatable with respect to said stator to provide a first capacity adjusting means and axially slidable with respect to said rotor to provide a second capacity adjusting means independent of said first capacity adjusting means, a first and a second band selectin switch mechanically coupled to said second capacity adjusting means to adjust the capacity range of said first capacity adjusting means and select said circuit elements corresponding to a desired frequency band, and means coupled to said first capacity adjusting means to continuously vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency band.

11. An arrangement for tuning an electric cirsuit over a plurality of frequency bands, comprising a plurality of circuit elements, a variable capacitor having a stator and a complementary rotor, said rotor being angularly rotatable with respect to said stator to provide a first capacity adjusting means and axially slidable with respect to said rotor to provide a second capacity adjusting means independent of said first capacity adjusting means, first and second band selecting switches mechanically coupled by means of a differential lever mechanism to said second capacity adjusting means individually to adjust the capacity range of said first capacity adjusting means and select said circuit elements corresponding to a desired frequency band, and means coupled to said first capacity adjusting means to continuously vary the capacity of said capacitor through said adjusted capacity range to tune over said desired frequency band.

FREDERIK HENDRIK GUSDORF.

ALEXANDRE HOROWITZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

